The present invention relates to a method of manufacturing concrete and an apparatus therefor, and particularly, but not exclusively, relates to a method of manufacturing mass concrete and an apparatus therefor.
When mass concrete members used for dams, bridges, reactor facilities, or the like, are constructed, cracking tends to occur in the mass concrete members due to temperature stresses caused by heat of hydration of the cement. Therefore, it is important to prevent such cracks to ensure uniform quality.
In order to prevent the cracks in mass concrete members, the following methods have been employed. For example, according to a so-called pre-cooling method, variations in the temperature of the concrete throughout the mass, which are caused by heat of hydration of cement, are reduced by decreasing the temperature of the concrete when mixing is completed. According to another conventional method, use is made of a concrete of higher strength, which also undergoes a temperature rise due to heat of hydration similar to that of ordinary concretes, but in which the higher strength of the concrete increases the resistance to cracks.
In the pre-cooling method, prior to the mixing the concrete components, each component is pre-cooled, using cool water, cool air, or ice, so as to lower the temperature of the concrete at the end of mixing. The cooled components are then mixed so that cracks caused by thermal stresses can be prevented.
Recently, particles of ice have been used in place of water for mixing concrete, so as to uniformly disperse the components of the concrete, thereby enhancing the strength of the concrete while lowering the temperature of the concrete at the end of mixing by latent heat of the ice in the same manner as in the pre-cooling method.
However, in the above conventional methods of preventing cracks in mass concrete, the following problems arise. In the pre-cooling method, cool water, cool air, or ice is used as a coolant for cooling each component of the concrete. When the temperature of the concrete, at the end of mixing, must be lowered to a great extent, components may not be sufficiently cooled to a predetermined temperature. In addition, a considerable period of time is required to cool the components.
In the method wherein ice is used in place of water, particles of ice may remain in the concrete after mixing and the mixing time may be prolonged, depending on the size and amount of ice, and hence the amount of ice which may be used is limited. Therefore, the temperature of the concrete may not be sufficiently lowered as in the case of using cool water or cool air.